Who determines if John McCain is a Healthy Survivor? Whoever can determine if McCain is (1) getting good care and (2) living as fully as possible.
If you can determine whether McCain's care is based on sound information by qualified professionals, you can make an assessment about the first criterion of Healthy Survivorship.
Cutting-edge conventional medicine, despite all its limits and problems, is the foundation of good care. Healthy Survivors don't have to follow their specialists' recommendations; they only have to understand their medical condition and their conventional and investigational options for treating it.
Qualified physicians are essential, but not sufficient. "Good care" includes physician extenders and allied health professionals who help patients make medical decisions in keeping with their values and help patients optimize recovery, when possible, and comfort, always. McCain is bright and at a top center; he's surely getting good care.
To determine if McCain is living as fully as possible, only people who know him on a deeply personal level can possibly make that judgment. The media and the public who know only his public persona cannot know what constitutes living fully for McCain. As for McCain's decision to get back to work today, that's for McCain and his physicians (and loved ones) to work out. And his decision reflects his desire to live as fully as possible despite his cancer.
If McCain writes an article and/or does an interview to share his thoughts and feelings about his life with cancer, we all can pass judgment about the state of his survivorship.